3 replies to this topic

[schnowbie]

Hi Guys ..
I purchased an aftermarket problem for my BMW.
problem is, when I turn the car on, the warning lights will pop up regarding the headlights.

the problem is with the "angel eyes". it's connected as the parker lights.
it will turn on but after a while it will turn off ...
but low beam/indicators/high beam, works perfectly fine ... only the Angel eyes
could it be the resistor? that's what I heard anyway ...
this is the headlight for it ...

http://www.marsperfo...-E90-05-08.html

Thanks

[starlet666]

u will constanly run in2 troubles when modding anything in this car man, like all new euro's they run that crazy hitech canbus system, where u touch anything that changes the load on the system, it brings up warning lights for all kinds of things, commonly though the warnings it gives u arent even the parts that are causing the issue,


oh
and ur warranty will possibly be completely null and void on anything electrical in most cases now that u have put them headlights in because of the canbus system

Edited by starlet666, 24 July 2010 - 12:49 AM.

[7shades]

I'm pretty sure the LED angel eyes have lower resistance to the standard parkers.

Bulb failure lights work by sensing resistance across a circuit... A drop in resistance indicates a failed bulb so your system is getting confused. I'm not sure how the newer Beemers work but in most cars you have to either change the relays to LED specific ones, or solder a certain value resistor inline on the circuit you've changed to LED.

[shaun]

7shades, on 24 July 2010 - 09:21 AM, said:

I'm pretty sure the LED angel eyes have lower resistance to the standard parkers.

Bulb failure lights work by sensing resistance across a circuit... A drop in resistance indicates a failed bulb so your system is getting confused. I'm not sure how the newer Beemers work but in most cars you have to either change the relays to LED specific ones, or solder a certain value resistor inline on the circuit you've changed to LED.

The easy way around this problem is to calculate the resistance of the old globe when its on ( light globes resistance increase when they turn on) and put a resistor in parallel to trick the ECU into thinking they are still there.

To do this use the following;
Step 1: calculate the 'on' current of the light
I = P / V
Where P is the rating of the globe in Watts
V is the car voltage (13.8V approx due to alternator when car is running)
I is the current (what you want to calculate)

Eg: 5W globe

I = 5 / 13.8
=0.36 or 360mA

Step 2 : Use this current to calculate the resistance of the light when its on by

R = V / I
Where R is the resistance
I is the current ( from step 1)
V is the car voltage

Eg:
R = 13.8 / 0.36
= 38.3 Ohms

Step 3: put a 5W resistor of the same value (38 Ohms) in parallel with the LED cct. This will drop the total resistance of the cct to the same value (approx) of the old lights. The formula to work it out exactly is:

Rt = (R1R2)/(R1+R2)
Where Rt is the total cct resistance
R1 is the Old lights total resistance
R2 is resistor you need to put in parallel.

So for a LED light replacing a 5W globe youll need to solder a 38 Ohm resistor in parallel to the LED assembly. Do the same on both sides and then your done.

Use at least a 5W resistor as it will be drawing a fair amount of current. Ideally you should use a resistance with the same power rating as the light its replacing.
You'll end up drawing the same amount of current as the old setup but im guessing you did it for looks rather than efficeincy.

Its not vitally important that the resistor is exactly the same value as the calculations as most ECU's will have a fairly broad tolerances (thats why you can run higher rating globes without it giving you an error)

That should sort out your problem